EFFECT OF OLEIC ACID CONCENTRATION AS HYDROPHOBIC COMPONENT IN THE PRODUCTION OF SOPHOROLIPIDS BY Candida bombicola

Sophorolipid is a class of glycolipid produced by the Candida bombicola and has potential antimicrobial activity against Gram-negative and Gram-positive bacteria. The fermentation conditions utilized can modify their chemical structure. Sophorolipid presents a disaccharide (2´-O-β-D-glucopyranosyl-1-β-D-glucose) sophorose linked by a long-chain fatty acid, reaching up to 40 different types of isomers of the acidic and lactonic forms, these structures are produced in accordance and with the influence of the substrate provided. Therefore, the proportions produced of these forms is variable and the properties and applications of these sophorolipids are directly related to these formed structures. The aim of this study was to investigate the influence of oleic acid concentration in sophorolipids production by Candida bombicola ATCC 22214. Fermentations media contained (g.L-1): 50, 75 and 90 oleic acid; 77.5 glucose and 2.5 yeast extract. The process was carried in 250 mL Erlenmeyer flasks, containing 25 mL of different media, at 150 rpm, 30 ºC for 120h. At the end, the media was centrifugated at 13,050 g for 15 minutes and washed with ethyl-acetate to separate the biomass from the media. The consumed sugar was measured by the Somogyi-Nelson method and the yeast biomass, the consumed oleic acid content and the sophorolipids production were analyzed gravimetrically. The sophorolipids were obtained by liquid-liquid extraction using ethyl acetate, hexane and methanol. The results obtained in 50, 75 and 90 g.L-1 of oleic acid composition were, respectively: Sophorolipid production (g.L-1): 24.69, 25.81, 20.27; biomass (g.L-1): 10.19, 10.57, 9.36; consumed glucose (g.L-1): 37.16, 41.88, 39.07; and consumed oleic acid (g.L-1): 25.6, 31.41, 34.76. Besides the better production obtained in the media with 75 g.L-1 of oleic acid, the 50 g.L-1 media presented the better yield with 55.57% efficiency, while the 75 and 90 g.L-1 oleic content showed 49.64% and 40.13%, respectively. It is known that sophorolipids production occurs in presence of hydrophilic carbon source and in this study the oleic acid was a good substrate for the production, but the yield of sophorolipids is not directly proportional to added oleic acid. The decrease in the sophorolipid synthesis rate is probably due to accumulation of unused oleic acid, which inhibits microbial growth. This shows that a smaller concentration of oleic acid is favourable and continuous addition of substrate would be beneficial for production of sophorolipids than single time addition.